package cn.fanyamin.util.reflect;

/*
 * Copyright 2002-2009 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.springframework.util.Assert;


/**
 * Simple utility class for working with the reflection API and handling
 * reflection exceptions.
 *
 * <p>Only intended for internal use.
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rod Johnson
 * @author Costin Leau
 * @author Sam Brannen
 * @since 1.2.2
 */
public abstract class ReflectionUtils {

        /**
         * Attempt to find a {@link Field field} on the supplied {@link Class} with
         * the supplied <code>name</code>. Searches all superclasses up to {@link Object}.
         * @param clazz the class to introspect
         * @param name the name of the field
         * @return the corresponding Field object, or <code>null</code> if not found
         */
        public static Field findField(Class clazz, String name) {
                return findField(clazz, name, null);
        }

        /**
         * Attempt to find a {@link Field field} on the supplied {@link Class} with
         * the supplied <code>name</code> and/or {@link Class type}. Searches all
         * superclasses up to {@link Object}.
         * @param clazz the class to introspect
         * @param name the name of the field (may be <code>null</code> if type is specified)
         * @param type the type of the field (may be <code>null</code> if name is specified)
         * @return the corresponding Field object, or <code>null</code> if not found
         */
        public static Field findField(Class clazz, String name, Class type) {
                Assert.notNull(clazz, "Class must not be null");
                Assert.isTrue(name != null || type != null, "Either name or type of the field must be specified");
                Class searchType = clazz;
                while (!Object.class.equals(searchType) && searchType != null) {
                        Field[] fields = searchType.getDeclaredFields();
                        for (Field field : fields) {
                                if ((name == null || name.equals(field.getName())) &&
                                                (type == null || type.equals(field.getType()))) {
                                        return field;
                                }
                        }
                        searchType = searchType.getSuperclass();
                }
                return null;
        }

        /**
         * Set the field represented by the supplied {@link Field field object} on
         * the specified {@link Object target object} to the specified
         * <code>value</code>. In accordance with
         * {@link Field#set(Object, Object)} semantics, the new value is
         * automatically unwrapped if the underlying field has a primitive type.
         * <p>Thrown exceptions are handled via a call to
         * {@link #handleReflectionException(Exception)}.
         * @param field the field to set
         * @param target the target object on which to set the field
         * @param value the value to set; may be <code>null</code>
         */
        public static void setField(Field field, Object target, Object value) {
                try {
                        field.set(target, value);
                }
                catch (IllegalAccessException ex) {
                        handleReflectionException(ex);
                        throw new IllegalStateException(
                                        "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
                }
        }

        /**
         * Get the field represented by the supplied {@link Field field object} on
         * the specified {@link Object target object}. In accordance with
         * {@link Field#get(Object)} semantics, the returned value is
         * automatically wrapped if the underlying field has a primitive type.
         * <p>Thrown exceptions are handled via a call to
         * {@link #handleReflectionException(Exception)}.
         * @param field the field to get
         * @param target the target object from which to get the field
         * @return the field's current value
         */
        public static Object getField(Field field, Object target) {
                try {
                        return field.get(target);
                }
                catch (IllegalAccessException ex) {
                        handleReflectionException(ex);
                        throw new IllegalStateException(
                                        "Unexpected reflection exception - " + ex.getClass().getName() + ": " + ex.getMessage());
                }
        }

        /**
         * Attempt to find a {@link Method} on the supplied class with the supplied name
         * and no parameters. Searches all superclasses up to <code>Object</code>.
         * <p>Returns <code>null</code> if no {@link Method} can be found.
         * @param clazz the class to introspect
         * @param name the name of the method
         * @return the Method object, or <code>null</code> if none found
         */
        public static Method findMethod(Class clazz, String name) {
                return findMethod(clazz, name, new Class[0]);
        }

        /**
         * Attempt to find a {@link Method} on the supplied class with the supplied name
         * and parameter types. Searches all superclasses up to <code>Object</code>.
         * <p>Returns <code>null</code> if no {@link Method} can be found.
         * @param clazz the class to introspect
         * @param name the name of the method
         * @param paramTypes the parameter types of the method
         * (may be <code>null</code> to indicate any signature)
         * @return the Method object, or <code>null</code> if none found
         */
        public static Method findMethod(Class clazz, String name, Class... paramTypes) {
                Assert.notNull(clazz, "Class must not be null");
                Assert.notNull(name, "Method name must not be null");
                Class searchType = clazz;
                while (searchType != null) {
                        Method[] methods = (searchType.isInterface() ? searchType.getMethods() : searchType.getDeclaredMethods());
                        for (Method method : methods) {
                                if (name.equals(method.getName()) &&
                                                (paramTypes == null || Arrays.equals(paramTypes, method.getParameterTypes()))) {
                                        return method;
                                }
                        }
                        searchType = searchType.getSuperclass();
                }
                return null;
        }

        /**
         * Invoke the specified {@link Method} against the supplied target object
         * with no arguments. The target object can be <code>null</code> when
         * invoking a static {@link Method}.
         * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
         * @param method the method to invoke
         * @param target the target object to invoke the method on
         * @return the invocation result, if any
         * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
         */
        public static Object invokeMethod(Method method, Object target) {
                return invokeMethod(method, target, new Object[0]);
        }

        /**
         * Invoke the specified {@link Method} against the supplied target object
         * with the supplied arguments. The target object can be <code>null</code>
         * when invoking a static {@link Method}.
         * <p>Thrown exceptions are handled via a call to {@link #handleReflectionException}.
         * @param method the method to invoke
         * @param target the target object to invoke the method on
         * @param args the invocation arguments (may be <code>null</code>)
         * @return the invocation result, if any
         */
        public static Object invokeMethod(Method method, Object target, Object... args) {
                try {
                        return method.invoke(target, args);
                }
                catch (Exception ex) {
                        handleReflectionException(ex);
                }
                throw new IllegalStateException("Should never get here");
        }

        /**
         * Invoke the specified JDBC API {@link Method} against the supplied
         * target object with no arguments.
         * @param method the method to invoke
         * @param target the target object to invoke the method on
         * @return the invocation result, if any
         * @throws SQLException the JDBC API SQLException to rethrow (if any)
         * @see #invokeJdbcMethod(java.lang.reflect.Method, Object, Object[])
         */
        public static Object invokeJdbcMethod(Method method, Object target) throws SQLException {
                return invokeJdbcMethod(method, target, new Object[0]);
        }

        /**
         * Invoke the specified JDBC API {@link Method} against the supplied
         * target object with the supplied arguments.
         * @param method the method to invoke
         * @param target the target object to invoke the method on
         * @param args the invocation arguments (may be <code>null</code>)
         * @return the invocation result, if any
         * @throws SQLException the JDBC API SQLException to rethrow (if any)
         * @see #invokeMethod(java.lang.reflect.Method, Object, Object[])
         */
        public static Object invokeJdbcMethod(Method method, Object target, Object... args) throws SQLException {
                try {
                        return method.invoke(target, args);
                }
                catch (IllegalAccessException ex) {
                        handleReflectionException(ex);
                }
                catch (InvocationTargetException ex) {
                        if (ex.getTargetException() instanceof SQLException) {
                                throw (SQLException) ex.getTargetException();
                        }
                        handleInvocationTargetException(ex);
                }
                throw new IllegalStateException("Should never get here");
        }

        /**
         * Handle the given reflection exception. Should only be called if
         * no checked exception is expected to be thrown by the target method.
         * <p>Throws the underlying RuntimeException or Error in case of an
         * InvocationTargetException with such a root cause. Throws an
         * IllegalStateException with an appropriate message else.
         * @param ex the reflection exception to handle
         */
        public static void handleReflectionException(Exception ex) {
                if (ex instanceof NoSuchMethodException) {
                        throw new IllegalStateException("Method not found: " + ex.getMessage());
                }
                if (ex instanceof IllegalAccessException) {
                        throw new IllegalStateException("Could not access method: " + ex.getMessage());
                }
                if (ex instanceof InvocationTargetException) {
                        handleInvocationTargetException((InvocationTargetException) ex);
                }
                if (ex instanceof RuntimeException) {
                        throw (RuntimeException) ex;
                }
                handleUnexpectedException(ex);
        }

        /**
         * Handle the given invocation target exception. Should only be called if
         * no checked exception is expected to be thrown by the target method.
         * <p>Throws the underlying RuntimeException or Error in case of such
         * a root cause. Throws an IllegalStateException else.
         * @param ex the invocation target exception to handle
         */
        public static void handleInvocationTargetException(InvocationTargetException ex) {
                rethrowRuntimeException(ex.getTargetException());
        }

        /**
         * Rethrow the given {@link Throwable exception}, which is presumably the
         * <em>target exception</em> of an {@link InvocationTargetException}.
         * Should only be called if no checked exception is expected to be thrown by
         * the target method.
         * <p>Rethrows the underlying exception cast to an {@link RuntimeException}
         * or {@link Error} if appropriate; otherwise, throws an
         * {@link IllegalStateException}.
         * @param ex the exception to rethrow
         * @throws RuntimeException the rethrown exception
         */
        public static void rethrowRuntimeException(Throwable ex) {
                if (ex instanceof RuntimeException) {
                        throw (RuntimeException) ex;
                }
                if (ex instanceof Error) {
                        throw (Error) ex;
                }
                handleUnexpectedException(ex);
        }

        /**
         * Rethrow the given {@link Throwable exception}, which is presumably the
         * <em>target exception</em> of an {@link InvocationTargetException}.
         * Should only be called if no checked exception is expected to be thrown by
         * the target method.
         * <p>Rethrows the underlying exception cast to an {@link Exception} or
         * {@link Error} if appropriate; otherwise, throws an
         * {@link IllegalStateException}.
         * @param ex the exception to rethrow
         * @throws Exception the rethrown exception (in case of a checked exception)
         */
        public static void rethrowException(Throwable ex) throws Exception {
                if (ex instanceof Exception) {
                        throw (Exception) ex;
                }
                if (ex instanceof Error) {
                        throw (Error) ex;
                }
                handleUnexpectedException(ex);
        }

        /**
         * Throws an IllegalStateException with the given exception as root cause.
         * @param ex the unexpected exception
         */
        private static void handleUnexpectedException(Throwable ex) {
                throw new IllegalStateException("Unexpected exception thrown", ex);
        }

        /**
         * Determine whether the given method explicitly declares the given exception
         * or one of its superclasses, which means that an exception of that type
         * can be propagated as-is within a reflective invocation.
         * @param method the declaring method
         * @param exceptionType the exception to throw
         * @return <code>true</code> if the exception can be thrown as-is;
         * <code>false</code> if it needs to be wrapped
         */
        public static boolean declaresException(Method method, Class exceptionType) {
                Assert.notNull(method, "Method must not be null");
                Class[] declaredExceptions = method.getExceptionTypes();
                for (Class declaredException : declaredExceptions) {
                        if (declaredException.isAssignableFrom(exceptionType)) {
                                return true;
                        }
                }
                return false;
        }


        /**
         * Determine whether the given field is a "public static final" constant.
         * @param field the field to check
         */
        public static boolean isPublicStaticFinal(Field field) {
                int modifiers = field.getModifiers();
                return (Modifier.isPublic(modifiers) && Modifier.isStatic(modifiers) && Modifier.isFinal(modifiers));
        }

        /**
         * Determine whether the given method is an "equals" method.
         * @see java.lang.Object#equals
         */
        public static boolean isEqualsMethod(Method method) {
                if (method == null || !method.getName().equals("equals")) {
                        return false;
                }
                Class[] paramTypes = method.getParameterTypes();
                return (paramTypes.length == 1 && paramTypes[0] == Object.class);
        }

        /**
         * Determine whether the given method is a "hashCode" method.
         * @see java.lang.Object#hashCode
         */
        public static boolean isHashCodeMethod(Method method) {
                return (method != null && method.getName().equals("hashCode") &&
                                method.getParameterTypes().length == 0);
        }

        /**
         * Determine whether the given method is a "toString" method.
         * @see java.lang.Object#toString()
         */
        public static boolean isToStringMethod(Method method) {
                return (method != null && method.getName().equals("toString") &&
                                method.getParameterTypes().length == 0);
        }


        /**
         * Make the given field accessible, explicitly setting it accessible if necessary.
         * The <code>setAccessible(true)</code> method is only called when actually necessary,
         * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
         * @param field the field to make accessible
         * @see java.lang.reflect.Field#setAccessible
         */
        public static void makeAccessible(Field field) {
                if (!Modifier.isPublic(field.getModifiers()) ||
                                !Modifier.isPublic(field.getDeclaringClass().getModifiers())) {
                        field.setAccessible(true);
                }
        }

        /**
         * Make the given method accessible, explicitly setting it accessible if necessary.
         * The <code>setAccessible(true)</code> method is only called when actually necessary,
         * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
         * @param method the method to make accessible
         * @see java.lang.reflect.Method#setAccessible
         */
        public static void makeAccessible(Method method) {
                if (!Modifier.isPublic(method.getModifiers()) ||
                                !Modifier.isPublic(method.getDeclaringClass().getModifiers())) {
                        method.setAccessible(true);
                }
        }

        /**
         * Make the given constructor accessible, explicitly setting it accessible if necessary.
         * The <code>setAccessible(true)</code> method is only called when actually necessary,
         * to avoid unnecessary conflicts with a JVM SecurityManager (if active).
         * @param ctor the constructor to make accessible
         * @see java.lang.reflect.Constructor#setAccessible
         */
        public static void makeAccessible(Constructor ctor) {
                if (!Modifier.isPublic(ctor.getModifiers()) ||
                                !Modifier.isPublic(ctor.getDeclaringClass().getModifiers())) {
                        ctor.setAccessible(true);
                }
        }


        /**
         * Perform the given callback operation on all matching methods of the
         * given class and superclasses.
         * <p>The same named method occurring on subclass and superclass will
         * appear twice, unless excluded by a {@link MethodFilter}.
         * @param targetClass class to start looking at
         * @param mc the callback to invoke for each method
         * @see #doWithMethods(Class, MethodCallback, MethodFilter)
         */
        public static void doWithMethods(Class targetClass, MethodCallback mc) throws IllegalArgumentException {
                doWithMethods(targetClass, mc, null);
        }

        /**
         * Perform the given callback operation on all matching methods of the
         * given class and superclasses.
         * <p>The same named method occurring on subclass and superclass will
         * appear twice, unless excluded by the specified {@link MethodFilter}.
         * @param targetClass class to start looking at
         * @param mc the callback to invoke for each method
         * @param mf the filter that determines the methods to apply the callback to
         */
        public static void doWithMethods(Class targetClass, MethodCallback mc, MethodFilter mf)
                        throws IllegalArgumentException {

                // Keep backing up the inheritance hierarchy.
                do {
                        Method[] methods = targetClass.getDeclaredMethods();
                        for (Method method : methods) {
                                if (mf != null && !mf.matches(method)) {
                                        continue;
                                }
                                try {
                                        mc.doWith(method);
                                }
                                catch (IllegalAccessException ex) {
                                        throw new IllegalStateException(
                                                        "Shouldn't be illegal to access method '" + method.getName() + "': " + ex);
                                }
                        }
                        targetClass = targetClass.getSuperclass();
                }
                while (targetClass != null);
        }

        /**
         * Get all declared methods on the leaf class and all superclasses.
         * Leaf class methods are included first.
         */
        public static Method[] getAllDeclaredMethods(Class leafClass) throws IllegalArgumentException {
                final List<Method> methods = new ArrayList<Method>(32);
                doWithMethods(leafClass, new MethodCallback() {
                        public void doWith(Method method) {
                                methods.add(method);
                        }
                });
                return methods.toArray(new Method[methods.size()]);
        }


        /**
         * Invoke the given callback on all fields in the target class,
         * going up the class hierarchy to get all declared fields.
         * @param targetClass the target class to analyze
         * @param fc the callback to invoke for each field
         */
        public static void doWithFields(Class targetClass, FieldCallback fc) throws IllegalArgumentException {
                doWithFields(targetClass, fc, null);
        }

        /**
         * Invoke the given callback on all fields in the target class,
         * going up the class hierarchy to get all declared fields.
         * @param targetClass the target class to analyze
         * @param fc the callback to invoke for each field
         * @param ff the filter that determines the fields to apply the callback to
         */
        public static void doWithFields(Class targetClass, FieldCallback fc, FieldFilter ff)
                        throws IllegalArgumentException {

                // Keep backing up the inheritance hierarchy.
                do {
                        // Copy each field declared on this class unless it's static or file.
                        Field[] fields = targetClass.getDeclaredFields();
                        for (Field field : fields) {
                                // Skip static and final fields.
                                if (ff != null && !ff.matches(field)) {
                                        continue;
                                }
                                try {
                                        fc.doWith(field);
                                }
                                catch (IllegalAccessException ex) {
                                        throw new IllegalStateException(
                                                        "Shouldn't be illegal to access field '" + field.getName() + "': " + ex);
                                }
                        }
                        targetClass = targetClass.getSuperclass();
                }
                while (targetClass != null && targetClass != Object.class);
        }

        /**
         * Given the source object and the destination, which must be the same class
         * or a subclass, copy all fields, including inherited fields. Designed to
         * work on objects with public no-arg constructors.
         * @throws IllegalArgumentException if the arguments are incompatible
         */
        public static void shallowCopyFieldState(final Object src, final Object dest) throws IllegalArgumentException {
                if (src == null) {
                        throw new IllegalArgumentException("Source for field copy cannot be null");
                }
                if (dest == null) {
                        throw new IllegalArgumentException("Destination for field copy cannot be null");
                }
                if (!src.getClass().isAssignableFrom(dest.getClass())) {
                        throw new IllegalArgumentException("Destination class [" + dest.getClass().getName() +
                                        "] must be same or subclass as source class [" + src.getClass().getName() + "]");
                }
                doWithFields(src.getClass(), new FieldCallback() {
                        public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
                                makeAccessible(field);
                                Object srcValue = field.get(src);
                                field.set(dest, srcValue);
                        }
                }, COPYABLE_FIELDS);
        }


        /**
         * Action to take on each method.
         */
        public static interface MethodCallback {

                /**
                 * Perform an operation using the given method.
                 * @param method the method to operate on
                 */
                void doWith(Method method) throws IllegalArgumentException, IllegalAccessException;
        }


        /**
         * Callback optionally used to method fields to be operated on by a method callback.
         */
        public static interface MethodFilter {

                /**
                 * Determine whether the given method matches.
                 * @param method the method to check
                 */
                boolean matches(Method method);
        }


        /**
         * Callback interface invoked on each field in the hierarchy.
         */
        public static interface FieldCallback {

                /**
                 * Perform an operation using the given field.
                 * @param field the field to operate on
                 */
                void doWith(Field field) throws IllegalArgumentException, IllegalAccessException;
        }


        /**
         * Callback optionally used to filter fields to be operated on by a field callback.
         */
        public static interface FieldFilter {

                /**
                 * Determine whether the given field matches.
                 * @param field the field to check
                 */
                boolean matches(Field field);
        }


        /**
         * Pre-built FieldFilter that matches all non-static, non-final fields.
         */
        public static FieldFilter COPYABLE_FIELDS = new FieldFilter() {
                public boolean matches(Field field) {
                        return !(Modifier.isStatic(field.getModifiers()) ||
                                        Modifier.isFinal(field.getModifiers()));
                }
        };

}
